Java Reference
In-Depth Information
This principle carries on for another three
if
statements, in which you also check for Chrome, Safari, and
Opera. If you have a browser you want to check for, this is the place to add its
if
statement. Just view the
string it returns in
navigator.userAgent
and look for its name or something that uniquely identifies it.
If none of the
if
statements match, you return
UNKNOWN
as the browser name:
else {
return "UNKNOWN";
}
Now turn to the final function,
getBrowserVersion()
.
The browser version details often appear in the
userAgent
string right after the name of the browser.
For these reasons, your first task in the function is to find out which browser you are dealing with. You
declare and initialize the
browser
variable to the name of the browser, using the
getBrowserName()
function you just wrote:
function getBrowserVersion() {
var ua = navigator.userAgent;
var browser = getBrowserName();
If the browser is MSIE (Internet Explorer), you need to use the
userAgent
property again. Under IE,
the
userAgent
property always contains
MSIE
followed by the browser version. So what you need to do
is search for
MSIE
, and then get the number following that.
You set
findIndex
to the character position of the browser name plus the length of the name, plus
one. Doing this ensures you to get the character after the name and just before the version number.
browserVersion
is set to the floating‐point value of that number, which you obtain using the
substring()
method. This selects the characters starting at
findIndex
and ending with the one before
findIndex
, plus three. This ensures that you just select three characters for the version number:
var findIndex = ua.indexOf(browser) + browser.length + 1;
var browserVersion = parseFloat(ua.substring(findIndex, findIndex + 3));
If you look back to the
userAgent
strings, you see that IE10's is similar to this:
Mozilla/5.0 (compatible; MSIE 10.0; Windows NT 6.3; WOW64; Trident/7.0)
So
findIndex
will be set to the character index of the number
10
following the browser name.
browserVersion
will be set to three characters from and including the
10
, giving the version number as
10.0
.
At the end of the function, you return
browserVersion
to the calling code, as shown here:
return browserVersion;
}
You've seen the supporting functions, but how do you make use of them? Well, in the following code you
obtain two bits of information—browser name and version—and use these to filter which browser the
user is running:
var browserName = getBrowserName();
var browserVersion = getBrowserVersion();
if (browserName == "MSIE") {
